1. Field of the Invention
The present invention relates to a linkage-type keying device, particularly to a metallic linkage-type keying device.
2. Description of the Related Art
ESD (Electro Static Discharge) is usually the source of the electrical overstress, which damages electronic elements or systems. ESD usually causes external damages in semiconductor elements and disables electronic products.
ESD is likely to hit the interior of electronic products via penetrating through the assemblage gaps of electronic products. In a camera, the keys thereof are usually the gap-forming locations. The conventional keying device is often a one-piece design having a plastic linkage and plastic keys. In order to prevent the attack of ESD that penetrates through the gaps around keys, metallic plates are disposed in the perimeter of keys to guide ESD to the ground lest ESD attack the interior of electronic products. Refer to FIG. 1(a) and FIG. 1(b) sectional views schematically showing that metallic plates are disposed in the perimeter of a keying device of a camera. There are two methods to dispose metallic plates 4 in the perimeter of a key 10. One is to dispose the metallic plates 4 between a plastic linkage 6 and a camera casing 8, as shown in FIG. 1(a). The other is to dispose the metallic plate 4 at the bottom of the plastic linkage 6, as shown in FIG. 1(b). In addition to the plastic linkage 6, which is thicker originally, the installation of the metallic plates 4 makes the conventional keying device 2 occupy more space; thus, not only the camera needs a larger volume, but also the keys 10 become larger and have higher mold and material costs. Accordingly, the present invention proposes a compact and ESD-proof metallic linkage-type keying device.